Chapter 16

Select all of the events that occur during the latency period of HIV infection.

Viruses are released from macrophages by budding. The viral genome copy remains integrated into the host DNA. New virus particles are made.

Precursor molecules may have been protected from damaging UV rays by

being enclosed in bubbles

Bacterial cells divide by a process known as ______.

binary fission

On certain substrates, bacteria can form layers that create a microenvironment for the bacteria's growth. These layers are called

biofilms

During the latency period of HIV infection, before the onset of AIDS, how do new HIV particles exit host cells?

budding

Select all of the characteristics of the lambda phage.

can exist as a lysogenic or lytic virus infects E. coli can undergo lysogeny

Select all of the ways that microspheres are similar to cells.

can incorporate other molecules and energy can increase in size have a membrane-like boundary

In some bacteria, a gelatinous layer called the ______ lies outside the bacterial cell wall and membrane.

capsule

Select all of the following that apply to SARS.

caused by coronavirus pneumonia-like symptoms host is the Chinese horseshoe bat

Because they have a two-layer outer boundary, can divide, and can incorporate molecules, microspheres resemble

cells

A deep-sea vent prokaryote that oxidizes hydrogen sulfide to obtain energy is an example of a

chemoautotroph.

Spherical-shaped bacterial cells are referred to as

cocci

Bacteria exchange plasmids between cells in a process called ______.

conjugation

Match each mechanism of obtaining genetic information in bacteria with its correct description.

conjugation: transfer of plasmids between bacterial cells transfer of plasmids between bacterial cells transformation: uptake of DNA from the environment uptake of DNA from the environment bacteriophage infection: transfer of genetic material from a bacterial virus to a bacterial cell transfer of genetic material from a bacterial virus to a bacterial cell

Among the most prominent of the photosynthetic bacteria are the filamentous ______.

cyanobacteria

The oxygen in our atmosphere was originally produced by

cyanobacteria

When HIV infects T cells, the T cells are

destroyed because HIV exits the cells by lysing them.

After integrating into the host cell's DNA, the DNA copy of the HIV RNA

directs the production of new viral components.

Select all of the examples of emerging viruses.

ebola virus influenza West Nile virus

Viruses that originate in one organism, pass to another organism, and cause a disease in the other organism are called ______.

emerging viruses

Animal viruses can enter the cell whole and intact by being engulfed during the process of ______.

endocytosis

What structures allow bacteria to survive harsh conditions, such as dryness or high temperatures?

endospores

What hypothesis for the origin of life is the only one that is scientifically testable and could be disproved by experiment?

evolution

Select all of the characteristics of eukaryotes.

extensive internal compartmentalization cell division by mitosis flagella composed of 9 + 2 arrangement of microtubules DNA contained in a nucleus

Select components of early Earth that may have been present at ocean edges to promote the formation of complex organic molecules.

ionizing radiation ultraviolet radiation bubbles simple organic molecules

If the Earth formed at midnight in a 24-hour clock of biological time, what is the earliest time that the first cells would be present on Earth?

just before noon

Select all the sources that likely provided the energy to push electrons to higher energy levels in the hydrogen-rich gases of early Earth.

lightning the sun

Just outside the cell wall, some bacterial cells have a protective outer membrane composed of

lipopolysaccharide

When bacteriophages enter the lytic cycle, they

lyse and kill the infected host cell.

The presence of toxin genes in several types of bacterial pathogens is due to

lysogenic conversion.

When HIV particles enter the human body, what type of cells do they first infect?

macrophages

Early in an HIV infection, the HIV particles enter ______ by using a coreceptor called ______ that passes the gp120-CD4 complex through the membrane.

macrophages; CCR5

Select all of the processes used by different types of animal viruses to enter host cells.

membrane fusion endocytosis

What key reactants of the Miller-Urey experiment may have been destroyed by UV radiation in the absence of protective ozone?

methane ammonia

Anaerobic prokaryotic cells that use hydrogen gas to reduce carbon dioxide to CH4 are called

methanogens.

Carbon-rich macromolecules will sometimes gather in water to form ______ that shield the hydrophobic regions of the molecules from water.

microspheres

Spontaneous aggregations of macromolecules that form in a solution and have some cell-like qualities are called

microspheres

Gram-______ bacteria have a thin cell wall and possess an outer membrane made of lipopolysaccharides.

negative

Heterocysts are important in cyanobacteria for performing ______.

nitrogen fixation

Nitrogen in the atmosphere is not in a form that is usable by organisms. The process that converts this nitrogen to a usable form is known as ______ and can only be performed by a few species of ______.

nitrogen fixation; bacteria

Chemoautotrophs are prokaryotes that

obtain energy by oxidizing inorganic substances, such as ammonia or hydrogen gas.

Which of the following are examples of ways that chemoautotrophic prokaryotes obtain energy?

oxidizing sulfur oxidizing ammonia to form nitrate

Biological molecules may have been able to form on Earth due to the absence of _____________ in the atmosphere, which today quickly soaks up high-energy electrons.

oxygen

Prokaryotic cells are extremely important because photosynthetic bacteria were responsible for the introduction of ______ into our atmosphere.

oxygen

Bacterial cell walls are composed of

peptidoglycan.

Prokaryotes called ______ obtain energy from light and carbon from organic molecules, while prokaryotes called ______ obtain both energy and carbon atoms from organic molecules.

photoheterotrophs; chemoheterotrophs

Photoautotrophic prokaryotes use the energy of sunlight to build organic molecules from carbon dioxide through the process of

photosynthesis

Select all of the following that are natural reservoirs of the influenza virus.

pig ducks chickens

Bacteria may possess short, external structures for attachment called ______.

pili

Genetically-modified bacteria can be used to do which of the following? Select all that apply.

produce a protein that is toxic to crop pests produce medically-important proteins, like insulin remove pollutants

Which of the following describe a role prokaryotes play in the ecosystem?

produce oxygen through photosynthesis cause deadly diseases in plants and animals cycling minerals

What were the first life-forms to evolve?

prokaryotes

Match each feature of prokaryotes and eukaryotes with its correct description.

prokaryotic flagellum: composed of single fiber of protein that is spun eukaryotic flagellum: consists of 9 + 2 arrangement of microtubules that whip back and forth prokaryotic cell division: binary fission eukaryotic cell division: mitosis

During the lysogenic cycle a bacteriophage integrates its nucleic acid into the genome of the host. This combined genetic material, consisting of both host and bacteriophage, is called a

prophage

Lambda phage can enter the lysogenic cycle, meaning that it can exist as a

prophage

The structure of a virus consists of a nucleic acid, such as DNA or RNA and a capsid made of .

proteins

Photoheterotrophic prokaryotes include ______, while chemoheterotrophic prokaryotes include ______.

purple nonsulfur bacteria; decomposers

The single-stranded copy of the plasmid that is passed from the donor cell to the recipient cell is ______.

replicated by the recipient cell

What viral enzyme is able to synthesize complementary DNA from the virus RNA?

reverse transcriptase

Newly synthesized HIV particles exit human T cells by

rupturing the plasma membrane

T3 and T7 bacteriophages are different from T-even bacteriophages in that they have ______.

shorter tails

Select all of the following that are characteristics of plasmids.

small circular fragment of DNA passed to another cell during conjugation often contain genes conferring antibiotic resistance

Select the true statements about the viral enzyme reverse transcriptase.

synthesizes DNA using viral RNA as a template creates many new mutations in the HIV genome due to its inaccuracy

A filamentous virus with lethality rates up to 90% in some cases is ______.

the Ebola virus

The reproductive cycle in which the viral genome becomes incorporated into the bacterial chromosome is called

the lysogenic cycle

The reproductive cycle in which a bacteriophage ruptures and kills the infected host cell is called

the lytic cycle.

Select all of the following that are archaeans.

thermoacidophiles methanogens extremophiles

Archaeans that are found in hot springs with acidic water are known as

thermoacidophiles.

Select ways that bacteria can obtain genetic information.

transformation from bacterial viruses conjugation

Select all of the following that apply to the West Nile virus.

transmitted by mosquitos peak cases in the United States were in 2002

Select all of the following that are human bacterial diseases.

tuberculosis pneumonia plague cholera

A bacteriophage is a

virus that infects bacteria.

______ virus is common in the tropics and can result in microcephaly in newborns.

zika

A group of prokaryotes called ______ includes methanogens, but most described species of prokaryotes belong to the group called ______.

Archaea; Bacteria

What type of bacteria has been used as a biological control agent because it produces a protein that is toxic to insects?

Bacillus thuringiensis

In addition to CD4, what coreceptor does HIV require to be able to enter macrophages?

CCR5

HIV particles attach to cells with ______ receptors that precisely match the shapes of the ______ on the surface of HIV.

CD4; gp120 proteins

Due to mutations caused by reverse transcriptase, HIV eventually becomes able to infect T cells by binding to a coreceptor called ______ present on the surface of the cells.

CXCR4

Why is penicillin, which attacks the bacterial cell wall, effective only against gram-positive bacteria?

Gram-positive bacteria do not have an outer protective membrane.

What virus is believed to have evolved from similar viruses found in apes?

HIV

White blood cells called macrophages in humans are the first types of cells infected by

HIV particles.

Put the following steps in the order that they may have occurred according to the bubble model for the origin of complex organic molecules. Begin with the earliest step at the top.

1. The eruption of volcanoes under the sea released simple gases into bubbles 2. Methane and ammonia were protected inside bubbles that reflected UV rays and reacted to form amino acids 3. The bubbles pop at the surface of the ocean and release their contents into the atmosphere 4. Energy sources in the atmosphere promoted reactions that formed more complex organic molecules 5. Complex organic molecules could again be enclosed in bubbles at the sea surface and undergo further reactions within the protected bubbles

Arrange the steps of conjugation in the correct order, beginning with the first step at the top.

1. a conjugation bridge forms 2. the plasmid in the donor cell begins to replicate 3. a copy of the plasmid begins to pass across the conjugation bridge to the recipient cells 4. both cells use the single-stranded copy of the plasmid to complete the synthesis of a complementary plasmid strand 5. the recipient and donor cells both contain a complete copy of the plasmid

Put the steps of T4 bacteriophage infection of a bacterial cell into the correct order, beginning with the first step at the top.

1. tail fibers attach to the host bacterial cell wall 2. the bacteriophage tail contracts 3. the tail tube pierces the bacterial cell wall 4. DNA is injected into the cell 5. Viral DNA is transcribed 6. new phages are assembled and released from the cell

Select ways that prokaryotes play a key role in ecosystems.

A few types of bacteria can fix atmospheric nitrogen. Some prokaryotes are able to return elements to the environment. Some prokaryotes are decomposers.

Human immunodeficiency virus (HIV) is the infectious agent that causes ______ in humans, although symptoms of the disease do not usually appear for ______.

AIDS; 8-10 years

What component of the T4 bacteriophage passes into a bacterial cell?

DNA

A virus is ______.

DNA or RNA wrapped in a protein coat

Miller and Urey reconstructed ______ and found that organic molecules that are the building blocks of organisms could form under those conditions.

Earth's early atmosphere

Select all of the following that describe the lysogenic cycle of a bacteriophage.

Lysogeny occurs. The virus becomes a stable part of the host cell genome. A prophage forms.

The first information storage molecule was likely ______ because it can act as an enzyme and catalyze its own assembly.

RNA

The first macromolecule on Earth may have been __________ which may have been capable of catalyzing the formation of the first proteins.

RNA

Select reasons why RNA is thought to have been the first information storage molecule.

RNA was likely the first macromolecule. RNA can catalyze its own assembly.

When HIV infects T cells of the human body, why does this lead to the onset of acquired immunodeficiency (AIDS)?

T cells are important immune system cells that fight infections in the body.

A serious bacterial respiratory disease caused by a species of Mycobacterium is

TB

Select all of the following that are true about disease-causing bacteria.

TB and anthrax can be spread through the air. Some bacterial diseases are lethal to humans. Bacteria can cause diseases in plants.

Select all of the following that describe the lytic cycle of a bacteriophage.

The virus lyses the host cell. New virus particles are made.

How did researchers determine that tobacco mosaic virus (TMV) was composed of only RNA and protein?

When they reassembled RNA and protein that had been isolated from TMV, the reconstructed TMV was fully able to infect tobacco plants.

Select all of the characteristics of gram-positive bacteria.

a purple color after Gram staining a thick layer of peptidoglycan in their cell wall

A plasmid is ______.

a small, circular fragment of DNA

The bacteria that contain an outer membrane have

a thin cell wall

The experiment performed by Stanley Miller and Harold Urey demonstrated that on the early Earth, ______ could form from atmospheric gases and a source of energy.

amino acids

Although the Miller-Urey experiment demonstrated the spontaneous formation of ______, some scientists argue that the hydrogen-rich reactants may have been destroyed by damaging ______ present in early Earth.

amino acids; UV radiation

Select all the molecules likely to have been present in the atmosphere of early Earth, before life evolved.

ammonia methane hydrogen sulfide

Select all of the components that can be present in animal viruses.

an envelope enzymes more than one strand of genetic material a capsid

The chemical reactions that formed complex organic molecules on early Earth likely took place

at frothy ocean edges.

What phase of HIV infection requires that the gp120 spike proteins on HIV precisely fit the shape of CD4 receptors on human macrophages?

attachment

Metabolically, prokaryotes may be ______ and obtain carbon atoms from inorganic CO2, or they may be ______ and obtain some of their carbon atoms from organic molecules like glucose.

autotrophs; heterotrophs

Rod-shaped bacterial cells are referred to as

bacilli

Match each hypothesis for the origin of life on Earth with its correct description.

extraterrestrial origin: Life may have been carried to Earth from a distant planet or star. Life may have been carried to Earth from a distant planet or star. special creation: Life was put on Earth by supernatural or divine forces. Life was put on Earth by supernatural or divine forces. evolution: Gradual change as inanimate molecules became more and more complex and eventually gave rise to life. Gradual change as inanimate molecules became more and more complex and eventually gave rise to life.

Select all of the following that are characteristics of viruses.

extremely small protein coat surrounds genetic material contain DNA or RNA

Select all of the following that apply to the Ebola virus.

filovirus extremely lethal attacks connective tissue

A long, threadlike strand of protein used by bacteria for movement is called a(n)

flagella

What occurs when a viral gene is integrated into a bacterial chromosome and the bacterium expresses the viral gene?

gene conversion

Cyanobacteria perform nitrogen fixation in specialized cells known as

heterocysts.

Prokaryotes known as methanogens use ______ gas to reduce carbon dioxide and produce ______.

hydrogen; methane

Select all of the diseases that are caused by viruses.

influenza chicken pox polio herpes

After HIV enters a cell, the double-stranded DNA created by reverse transcriptase can

integrate into the host cell's DNA.